Seizure disorders are among the most frequently occurring neurologic disorders. Few studies provide comprehensive information on the incidence of the seizures by age, gender, seizure type or epilepsy syndrome, and none incorporate current EEG, CT, and MRI techniques into the diagnostic algorithm. An incidence study of all seizure disorders will be conducted in the island country of Iceland. This country has provided excellent medical care to its citizens at little or no cost for many years, and has an excellent medical record system as well as state of the art equipment for diagnosis and treatment. A comprehensive surveillance network will be established to identify all residents with newly diagnosed seizure disorders over a 4 year period. These cases will provide a comprehensive picture of the occurrence of seizure disorders in the population. Availability of current neurodiagnostic studies on most cases will provide accurate, reliable, and credible population data detailing the descriptive epidemiology of epilepsy. These data will satisfy criticisms of epidemiologic studies of epilepsy leveled by epileptologists and other clinicians. The classical conditions clinically identified as causes of epilepsy (brain trauma, cerebrovascular disease, infection of the central nervous system, tumor, neurologic abnormality from birth manifest by mental retardation or cerebral palsy) can be identified in only about 1/3 of all new cases of epilepsy. Few studies have been conducted on newly diagnosed cases of epilepsy to quantitate risk associated with these factors or to identify other factors which increase the risk for epilepsy. To identify potential risk factors for epilepsy these well characterized incidence cases will be matched to a control group selected from the general population. The study will provide further understanding of the mechanisms associated with established risk factors, allow examination of the role of putative risk factors (e.g., hypertension, depressive illness, alcohol use), and allow exploration of other potential risk factors. Results will lead to new concepts of epileptogensis in humans and to generally applicable interventions, resulting in a reduced frequency of epilepsy and associated neurologic co-morbidity.